PROJECT SUMMARY Ebola virus (EBOV) causes a severe disease in humans that is highly infectious. The 2013-2016 outbreak in West Africa resulted in over 28,000 infections and approximately 11,000 diagnostically confirmed fatalities. Almost two years after the conclusion of the outbreak, there are still no licensed vaccines against EBOV, nor are there any therapeutic interventions in clinical trials. There is still a significant need for therapies against EBOV and other filoviruses, as outbreaks continue to occur. The 2017 outbreak in the Democratic Republic of Congo resulted in approximately 30 infected patients and only 4 fatalities, but it highlights that EBOV is still a pressing global health concern. Ebola virus disease (EVD) is characterized by systemic organ damage and a dysregulated immune response. The liver is an early target of infection, and liver damage is correlated with more negative outcomes in patients. Hepatocytes are the major cell type which is infected in the liver, and the host response to EBOV infection in hepatocytes is unknown. Surprisingly, there is a species of ebolavirus, known as Reston virus (RESTV), which is non-pathogenic in humans. In a mouse model of EVD, a major distinction between EBOV and RESTV infection was the restriction of infection from the liver in RESTV infected mice. Therefore, hepatic responses may be a critical component in the pathogenesis of EBOV. A better understanding of the human hepatic response to EBOV and RESTV infection may determine correlates of protection against EVD. A barrier to investigating human hepatic responses to EBOV infection is the lack of robust models. Primary human hepatocytes (PHHs) are difficult to maintain in culture, and immortalized hepatic carcinoma cells (HCCs) have aberrant antiviral responses compared to primary cells. We propose to utilize an induced pluripotent stem cell (iPSC)-based platform for the generation of primary-like hepatocytes. Using a well- established directed differentiation protocol, we are able to generate hepatocytes from iPSCs which express hepatic markers similarly to primary human samples. Therefore, we propose to investigate the human host response to EBOV and RESTV infection in iPSC-derived hepatocytes. By using a primary-like cell, we will be able to better understand the human immune response to infection while retaining the ability to easily generate and manipulate cells in vitro. We will use this established cell-based platform for the novel investigation of the human response to EBOV and RESTV infection. Altogether this study aims to identify facets of EBOV infection which can be targeted by therapeutics to alleviate severe disease in patients.